LASIK eye surgery uses pulses of laser light to shave off tissue from the cornea, reshaping it. A typical LASIK laser emits a 1.0-mm-diameter laser beam with a wavelength of 193 nm. Each laser pulse lasts 20 ns and contains 1.4 mJ of light energy.

a. What is the power of one laser pulse?
b. During the very brief time of the pulse, what is the intensity of the light wave?

a.70000 W

b. 8.9 x W/m²

Explanation:

a. In order to find power of one laser pulse:

P= U/Δt

where,

U=light energy

Δt=laser pulse

P=1.4 x /20 x =>70000 W

b. Given:

Radius: 5 x

Intensity of light wave is given by

I= P/a (a=πr²)

where I is intensity and P is the power through an area a

I= 70000 /  π(5 x )²

I= 8.9 x W/m²

answer: at 24 february, 2014 the population gets twice of its initial population.

explanation:

since we have given that

the population for alpha city, t years after january 1, 2004 is given as

first we find out the initial population, i.e. t=0,

so, our quadratic equation becomes,

according to question, we have said that if the population has twice its initial population, then it becomes

so, time taken to reach this above mentioned population is given by

now, we know that time can't be negative so, we take t=9.149 years.

hence, at 24 february, 2014 the population gets twice of its initial population.